During operation of an internal combustion engine, an air/fuel mixture is introduced into a combustion chamber and is subsequently ignited by a spark plug. That ignition causes an explosion which burns the air/fuel mixture and initiates the engine's power stroke. During the power stroke, a certain amount of burnt air/fuel mixture, typically referred to as blow-by gas, blows by the piston ring and leaks between the piston and cylinder wall such that it ends up in the engine crankcase. If these blow-by gases are not sufficiently removed from the crankcase, they can degrade the quality of the lubricating oil already present within the crankcase, as well as increase the crankcase pressure causing damage to engine components such as seals.
It is therefore known in the internal combustion engine art to use a positive crankcase ventilation (PCV) valve to vent the crankcase pressure and eventually reintroduce the blow-by gases into the combustion chamber. During their time in the crankcase and valve cover, the blow-by gases pick up and draw along a certain amount of fine oil mist such that they become entrained with the oil mist. The term ‘air/oil stream’ is broadly used herein to include any gas that is entrained with or otherwise carries some degree of oil or other lubrication. Examples of some gases that could be constituents of an ‘air/oil stream’ are air, unburnt air/fuel mixtures, burnt air/fuel mixtures (exhaust), and blow-by gases, to name but a few. This air/oil stream must be treated with an air/oil separator so that the oil or other lubricant can be removed before reusing them in the combustion chamber. If the air/oil stream is not treated, the entrained oil can negatively impact the combustion process when it mixes with a fresh air/fuel mixture, and the entrained oil can become deposited over the catalytic converter which can reduce its operating life.
Various types of air/oil separators have been developed, including cyclonic-type separators, baffles, deflectors, cloth filters, foam, and other types of oil scavenging devices. Some examples of air/oil separators are disclosed in U.S. Pat. Nos. 5,617,834, 6,234,154, 6,453,892, 6,475,255, 6,530,367 and 6,591,820 and European Patent Nos. EP 0 024 148 and EP 0 487 203.